The present disclosure relates to a speed change device that includes a first clutch and a second clutch disposed around the first clutch.
There has hitherto been known a speed change device that includes a clutch C3 constituted as a multi-plate friction hydraulic clutch and a clutch C4 constituted as a multi-plate friction hydraulic clutch and disposed on the inner side of the clutch C3 (see Japanese Patent Application Publication No. 2013-155849, for example). The clutches C3 and C4 of the speed change device share a drum member that includes an inner drum and an outer drum that has a base end portion welded to the outer periphery of a sidewall portion of the inner drum. The inner drum of the drum member has an inner tubular portion that supports a piston of the clutch C4 and a cancel plate that defines a centrifugal hydraulic pressure cancellation chamber together with the piston, an annular sidewall portion extended radially outward from one end of the inner tubular portion, and a short cylindrical fixation portion extended from the sidewall portion on the inner side with respect to a joint portion with the outer drum. A cancel plate of the clutch C3 is fastened to the fixation portion of the inner drum via a rivet together with a clutch drum of the clutch C4. The cancel plate defines a centrifugal hydraulic pressure cancellation chamber of the clutch C3 on the radially outer side with respect to the centrifugal hydraulic pressure cancellation chamber of the clutch C4. Further, the drum member has a cancellation chamber oil hole formed in the inner tubular portion of the inner drum so as to communicate with the centrifugal hydraulic pressure cancellation chamber of the clutch C4, and a cancellation chamber oil passage that extends in the radial direction to communicate with the centrifugal hydraulic pressure cancellation chamber of the clutch C4. The cancellation chamber oil hole and the cancellation chamber oil passage communicate with each other via a recessed portion formed in the inner peripheral surface of the inner tubular portion of the inner drum. The recessed portion communicates with a working oil supply oil passage provided inside the inner tubular portion. Consequently, in the speed change device, working oil from the working oil supply oil passage is allocated by the recessed portion to be supplied to the centrifugal hydraulic pressure cancellation chamber of the clutch C4 and the centrifugal hydraulic pressure cancellation chamber of the clutch C3.